In a next-generation radio mobile communication system represented by LTE (long term evolution), a radio base station device (hereinafter called “eNB”) constituting the radio mobile communication system is connected to an MME/SAE-GW device (base station control device), which is its higher-order device, and another base station device using an IP transmission path.
The interfaces between eNBs and between an eNB and an MME/SAE-GW device are called “X2 interfaces” and “S1 interfaces”, respectively. Interfaces between other devices are also discussed from the viewpoint of standardization (see 3GPP TR 23.882 3GPP System Architecture Evolution: Report on Technical Options and Conclusions and the like).
Although in such a system an interface between respective devices constituting a radio mobile communication system can generally be arbitrarily set at the starting time of system, its setting method is semi-fixed and it is difficult to modify it during the operation of the system. Therefore, if a mobile station device (UE) existing in the system performs a handover accompanying area movement, it is desired to prepare its handover line in advance in a system on the handover-allowing side when the handover is performed with eNBs under the control of an MME/SAE-GW device or if the handover is performed between system areas (service areas) across MME/SAE-GW devices. A handover source base station device (hereinafter called source eNB) can transfer down-link (DL) data for a mobile station, received from an MME/SAE-GW device to a handover target base station device (hereinafter called “target eNB) in units of transmission (e.g., in units of RLC-SDU) and the target eNB can transfer the received data via the handover process to a mobile station device (hereinafter called “UE”). For example, when a line with a handover source base station device is not activated yet, a handover process as described above may not be performed.
The basic configuration of eUTRA, the transmission route of user data at the time of a handover, and a sequence chart between devices at the time of a handover are illustrated in FIGS. 1, 2 and 3, respectively.
ENBs 11-1 and 11-2 and eNBs 11-2 and 11-3 are under the control of an MME/SAE gateway 10-1 and 10-2, respectively. The MME/SAE gateways 10-1 and 10-2 and the eNB 11-1 through 11-3 are connected by the S1 interface. The eNBs 11-1 through 11-3 are connected by the X2 interface. The network between the eNBs 11-1 through 11-3 is E-UTRAN.
FIG. 2 explains the transmission route of user data at the time of a handover. Firstly, it is assumed that a mobile station 13 is under the control of a source eNB 11-1. User data transmitted from a higher-order network is transferred to the source eNB 11-1 side and the user data is wirelessly transmitted from the source eNB 11-1 to the mobile station 13. Then, it is assumed that the mobile station 13 is handed over from the source eNB 11-1 to be under the control of a target eNB 11-2. Then, the source eNB 11-1 transmits the user data to the target eNB 11-2. The target eNB 11-2 transmits the received user data to the mobile station 13. In this case, interfaces between the MME/SAE gateway 10 and the source eNB 11-1/target eNB 11-2 are S1 interfaces. An interface between the source eNB 11-1 and the target eNB 11-2 is an X2 interface.
FIG. 3 is a sequence chart at the time of a handover.
Firstly, user data is transmitted from an MME/SAE gateway to a mobile station UE via a source eNB. When a handover (H.O.) is started, the user data is transferred from the source eNB to a target eNB and then is transmitted to the mobile station UE. When the handover process is completed, the mobile station UE is under the control of the target eNB and the user data is transmitted from the MME/SAE gateway to the mobile station UE via the target eNB.
It is assumed that if an H.O. request comes when, between eNBs, a source eNB does not store the IP address of a target eNB; that is, when an X2 interface is not established between eNBs, a handover is performed via an MME/SAE-GW between the source eNB and the target eNB (ex. R3-070695).
A user data transfer sequence in the case where an X2 interface is not established is illustrated in FIG. 4.
Firstly, user data is transmitted from an MME/SAE gateway to a mobile station UE via a source eNB. When a handover (H.O.) is started, the user data is transferred from the source eNB to a target eNB. However, since an X2 interface is not established between the source eNB and the target eNB, the user data is transmitted from the source eNB to the MME/SAE gateway and is transmitted to the target eNB via the MME/SAE gateway. When a handover process is completed, the user data is transmitted from the MME/SAE gateway to the mobile station UE via the target eNB.
As described above, in a handover operation accompanying the area movement of a mobile station, a H.O. process includes the transfer of user data between eNBs. It is one object of the handover process to enable UE to receive a series of user data (lossless handover) by this series of operations. However, as illustrated in FIG. 3, in order to activate a desired line when an inter-device interface is not activated, it is desired for a movement source device to recognize device information, such as an IP address, about a movement target device. Therefore, it is desired for respective devices to store respective device individual information (such as IP addresses and the like) constituting a line connection paying attention to a handover. (Alternatively, it is desired for respective devices to initially register the device information of all the component devices at the time of system activation and its extensibility is small.) However, since stored information (an IP address and the like) differs for each device and line setting between all the devices is not necessary, it becomes desired for setting/adjusting respective devices constituting a system according to an individual environment and much labor is required for an operator (for example, the design of a handover area/adjacent area and the like). Flexible correspondence to the extension of a system (the additional installment of devices and the modification of an operation form) becomes difficult.
Patent document 1 discloses a mobile telephone system for inquiring with a position information management center of the IP address of a network connection device connected to a radio base station in which a cellular phone to be called is positioned in the radio base station connected to the Internet via the network connection device and is connected to a communication line with a network connection device having the IP address.    Patent document 1: Japanese Laid-open Patent Publication No. 11-150753    Non-patent document 1: 3GPP TR 25. 912, [online], [retrieved on May 1, 2007], Internet <URL: http://www.3gpp.org/ftp/Specs/html-info/25-series.htm>    Non-patent document 2: 3GPP TS25. 331, [online], [retrieved on May 29, 2007], Internet <URL: http://www.3gpp.org/ftp/Specs/html-info/25-series htm>    Non-patent document 3: 3GPP TR23. 882, [online], [retrieved on May 29, 2007], Internet <URL: http://www.3gpp.org/ftp/Specs/html-info/23-series htm>    Non-patent document 4: 3GPP R3-070695, [online], [retrieved on May 29, 2007], Internet <URL: http://www.3gpp.org/ftp/tsg_ran/WG3_Iu//TSGR3—55bis/docs/>